<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=<device-width>, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button id="count">点我</button>
    <div id="show"></div>

    <script type="text/javascript">
        const a = (function() {
            let count = 0;
            let button = document.getElementById('count');
            button.onclick = function() {
                Event.trigger('add', count++);
            }
        })()

        const b = (function() {
            let div = document.getElementById('show');
            Event.listen('add', (count) => {
                div.innerHTML = count;
            })
        })()
    </script>
</body>
</html>